If you need for a view (and all its subviews) not to be focusable by assistive tech like VoiceOver, you can set its accessibilityElementsHidden property to true. This isn't needed very often, but it can be useful for certain custom experiences.

Twitter app in the Notifications section. There are two tabs. One for All, and one for Mentions. The content comes after the tabs in a horizontally scrollable paged view. When the Mentions tab is selected, and the focus is on the Mentions tab, if the user swipes to the right, VoiceOver will look for the next element from top-left to bottom-right. So it may try to focus the first element in the scroll view, which would be the first tweet from the